Modifications in Galileo's letter to Benedetto Castelli of December 1613: an attempt to soften the Church's accusations

Abstract

This paper aims to discuss Galileo's letter to Benedetto Castelli, found in the Royal Society library, in August 2018, by researcher Salvatore Ricciardo of the University of Bergamo. We will discuss mainly the changes that Galileo made in the text of the letter dated December 21, 1613. This letter was already well known to researchers in the field, however, Ricciardo's discovery brought new information about the history of Galileo's confrontation with the Inquisition, in its arduous struggle against Copernicanism and the liberation of science from religious dogmas. The discovery shows that Galileo modified the text by trying to soften his harsh criticism of the theologians of the time, who were against the idea of heliocentrism. The main justification given by the opponents of Copernicanism centered on the subversion of some passages of Holy Scripture, especially the passage of Joshua. Until Ricciardo's discovery, the most accepted idea was that some rival clerics had modified the letter in order that Galileo was more easily accused of heresy by the Inquisition Court and his texts banned by the Index. However, we can verify from the discovery that, in fact, modifications to the letter were made, but by Galileo himself, as a probable attempt to get rid of some charges that were being made against him. Finally, we will present a translation of the letter found by Ricciardo, commenting on the modifications made by Galileo in relation to the old version.